Japanese Laid-open Patent Publication No. 2010-259213 discloses an optical scanning apparatus in which a mirror part for reflecting incident light is rotated about a rotation axis by an actuator, which includes an upper electrode on an upper surface of a piezoelectric body and a lower electrode on a lower surface of the piezoelectric body, such that a scanning operation is performed with the reflected light. This actuator includes an upper wiring connecting to the upper electrode and a lower wiring connecting to the lower electrode in order to apply the voltage to the piezoelectric body.
FIG. 1 is a diagram for explaining the upper wiring of the actuator according to prior art. The actuator 10 illustrated in FIG. 1 has a multi-layered configuration such that the piezoelectric body is formed between the lower electrode 11 and the upper electrode 12. The lower electrode 11 is connected to a common lower wiring (not illustrated). The upper electrode 12 is connected to an upper wiring 13. According to the actuator 10, the piezoelectric body is driven by applying the voltage between the common lower wiring and the upper wiring 13.
Further, according to the prior art actuator 10 illustrated in FIG. 1, when the lower electrode 11 and the upper electrode 12 are layered, an end portion (outer edge) 11T of the lower electrode 11 under the upper electrode 12 extends off the upper electrode 12. Therefore, in the actuator 10, an insulating part 14 is formed such that it covers the end portion 11T of the lower electrode 11 where the upper wiring 13 is formed in order to prevent contact between the lower electrode 11 and the upper electrode 12.
According to the prior art technique, if the difference t3 between the width t1 of the insulating part 14 and the width t2 of the upper wiring is not sufficient, there may be risk that the insulating part 14 is broken when such a great voltage which generates potential difference between the lower electrode 11 and the upper electrode 12 is applied.